We propose a two-year study to determine the feasibility and applications of a selective-exposure radiographic technique based on a digitally-prepared beam-attenuation mask. Using low-dose patient-positioning images, a computer-driven dot-matrix printer employing a ribbon containing heavy-metal compounds will generate a beam-attenuating mask which can be accurately positioned between the patient and the x-ray tube. The transmitted x-ray beam may be prepared in such a way that fixed anatomical variations are either presubtracted for dynamic studies using contrast materials such as coronary cineangiography or digital subtraction angiography, or suppressed in order to reduce detector dynamic-range problems for applications such as chest radiography. The technique also will provide significant improvements in several physical parameters including scatter distribution, signal-to-noise ratio, image contrast, and patient dose-distribution. Specific aims include: (1) design and construction of the digital beam attenuator system, (2) evaluation of its effects on several physical image parameters using simple phantom experiments, (3) determination, by means of dog experiments, of whether the techniques should be developed further for application in digital subtraction angiography, static nonsubtraction radiography, and beam-subtraction angiography.